GHSA-4M4J-HMQQ-3GXM

Vulnerability from github – Published: 2026-06-19 19:35 – Updated: 2026-06-19 19:35
VLAI
Summary
symfony/ux-live-component: CSRF Protection Bypass — Accept Header is CORS-Safelisted
Details

Description

When using symfony/ux-live-component, methods annotated with #[LiveAction] are invokable from the browser and mutate server-side state via AJAX. Symfony\UX\LiveComponent\EventListener\LiveComponentSubscriber::isLiveComponentRequest() gated these invocations on the presence of Accept: application/vnd.live-component+html, with a code comment stating that this acted as a CSRF protection.

The Accept header is a CORS-safelisted request header, so a cross-origin fetch() can set it without triggering a preflight. The header therefore provided no CSRF protection. Any #[LiveAction] could be forged cross-origin against a victim's session.

In practice the attack is mitigated by SameSite=Lax session cookies (Symfony's default), but applications using SameSite=None, credentials: 'include' with a permissive cookie policy, or that have been pivoted from another same-origin vector remained exposed.

Resolution

isLiveComponentRequest() now additionally requires the request header X-Requested-With: XMLHttpRequest. This header is not CORS-safelisted, so the browser issues a preflight OPTIONS request for any cross-origin attempt; Symfony does not advertise CORS for LiveComponent endpoints, the preflight fails, and the real request is blocked before it reaches the application. The bundled Stimulus client already sends X-Requested-With on every LiveComponent request (RequestBuilder.ts), so standard usage is unaffected. Cross-origin callers must add X-Requested-With to their CORS Access-Control-Allow-Headers allow-list.

The patch for this issue is available here for branch 2.x (and forward-ported to 3.x).

Credits

Symfony would like to thank Anthropic (via Project Glasswing) for reporting the issue and Hugo Alliaume for providing the fix.

Severity
2.1 (Low)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "symfony/ux-live-component"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.22.0"
            },
            {
              "fixed": "2.36.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "symfony/ux-live-component"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "3.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-49215"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-352"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-19T19:35:01Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "### Description\n\nWhen using `symfony/ux-live-component`, methods annotated with `#[LiveAction]` are invokable from the browser and mutate server-side state via AJAX. `Symfony\\UX\\LiveComponent\\EventListener\\LiveComponentSubscriber::isLiveComponentRequest()` gated these invocations on the presence of `Accept: application/vnd.live-component+html`, with a code comment stating that this acted as a CSRF protection.\n\nThe `Accept` header is a [CORS-safelisted request header](https://fetch.spec.whatwg.org/#cors-safelisted-request-header), so a cross-origin `fetch()` can set it without triggering a preflight. The header therefore provided no CSRF protection. Any `#[LiveAction]` could be forged cross-origin against a victim\u0027s session.\n\nIn practice the attack is mitigated by `SameSite=Lax` session cookies (Symfony\u0027s default), but applications using `SameSite=None`, `credentials: \u0027include\u0027` with a permissive cookie policy, or that have been pivoted from another same-origin vector remained exposed.\n\n### Resolution\n\n`isLiveComponentRequest()` now additionally requires the request header `X-Requested-With: XMLHttpRequest`. This header is **not** CORS-safelisted, so the browser issues a preflight `OPTIONS` request for any cross-origin attempt; Symfony does not advertise CORS for LiveComponent endpoints, the preflight fails, and the real request is blocked before it reaches the application. The bundled Stimulus client already sends `X-Requested-With` on every LiveComponent request (`RequestBuilder.ts`), so standard usage is unaffected. Cross-origin callers must add `X-Requested-With` to their CORS `Access-Control-Allow-Headers` allow-list.\n\nThe patch for this issue is available [here](https://github.com/symfony/ux/commit/aed7493db2b4b7bf1f9c79b33cda544f06904b27) for branch 2.x (and forward-ported to 3.x).\n\n### Credits\n\nSymfony would like to thank Anthropic (via Project Glasswing) for reporting the issue and Hugo Alliaume for providing the fix.",
  "id": "GHSA-4m4j-hmqq-3gxm",
  "modified": "2026-06-19T19:35:01Z",
  "published": "2026-06-19T19:35:01Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/symfony/ux/security/advisories/GHSA-4m4j-hmqq-3gxm"
    },
    {
      "type": "WEB",
      "url": "https://github.com/symfony/ux/commit/aed7493db2b4b7bf1f9c79b33cda544f06904b27"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/ux-live-component/CVE-2026-49215.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/symfony/ux"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "symfony/ux-live-component: CSRF Protection Bypass \u2014 Accept Header is CORS-Safelisted"
}



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